When the combustion pressure of a liquid-propellant rocket engine is very high, it is no exaggeration to say that whether the cooling of the combustion chamber thereof is good or bad determines the performance and life of the engine. However, it is known that the conventional cooling system using forced convection is limited in its cooling ability. Particularly, in the reusable type high performance rocket engine, it is necessary to enhance the cooling ability in order to increase its life, but if an attempt is made to enhance the cooling ability by using the conventional system, it will lead to a greatly increased pressure loss in the cooling passages and an increased weight of the entire rocket engine, which in turn will result in reduced performance of the engine.